Memory is one type of integrated circuitry, and is used in computer systems for storing data. Integrated memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
Integrated circuit fabrication continues to strive to produce smaller and denser integrated circuits. Accordingly, there has been substantial interest in memory cells that can be utilized in cross-point architectures. Example types of memory cells that are suitable for utilization in cross-point architectures are resistive RAM (RRAM) cells, phase change RAM (PCRAM) cells, and programmable metallization cells (PMCs)—which may be alternatively referred to as a conductive bridging RAM (CBRAM) cells, nanobridge memory cells, or electrolyte memory cells. The memory cell types are not mutually exclusive. For example, RRAM may be considered to encompass PCRAM and PMCs.
The cross-point architectures may comprise memory cell material between a pair of electrodes. Various problems can be encountered in the development of such architectures. The problems can involve, for example, mask misalignment during the various patterning steps utilized to pattern the electrodes and the memory cell material. Each electrode may be patterned with a separate masking step, and the memory cell material may be patterned with yet another masking step. Thus, there can be at least three masking steps to align during the fabrication of the memory cells. As another example, the problems may involve difficulties in utilizing some types of memory cell materials. For instance, some memory cell materials comprise oxides which are reactive toward many conductive materials. Thus it can be desired to use noble metals (for instance, platinum, silver, etc.) in electrodes that contact such oxides. However, the non-reactivity of the noble metals can make them difficult to pattern.
It would be desirable to develop improvements in memory cell fabrication which alleviate one or more of the above-discussed problems, and to develop improved memory cells.